The present invention relates to a battery power source device having a desired output power and composed of a number of serially-connected rechargeable battery cells, and to a battery voltage detecting device for determining voltage of each block of serially-connected cells for monitoring the operating condition of the battery power source device.
It is known in the art to constitute a battery power source device by connecting a large number of cells in series to attain a larger output voltage, because discrete cells have only a small electromotive force of about 1V to 2V. All of the serially-connected cells constituting such battery power source device must be in a normal and uniform operating state, and hence it is necessary to monitor the operating state of each of the cells. Battery voltage is a significant factor for determining the operating state of the battery. Accurate detection of battery voltage enables determination of the operating state of the battery.
FIG. 7 shows the arrangement of a prior art battery voltage detecting device adapted for a battery power source device in a vehicle which uses an electric motor in combination with an internal combustion engine as a power source. Cells are divided into a plurality of blocks (hereinafter referred to as battery modules) respectively consisting of a plurality of serially connected cells, and voltages of respective battery modules are separately detected. A motor 30 is composed of a large number of serially connected nickel metal hydride rechargeable battery cells to output a drive power necessary for driving the vehicle. Accordingly, the electric circuit system for driving the motor 30 is a high-voltage electric circuit in comparison to the electric circuit system for driving the engine.
The electric circuit system for driving the engine is a conventional low-voltage electric circuit, and the ground potential thereof is insulated from that of the electric circuit system for driving the motor, so that the high-voltage electric circuit is floating.
As shown in FIG. 7, cells are serially connected in units of a predetermined number (twelve) to make up separate battery modules 19, and the battery power source device outputs a voltage obtained by all of the serially connected battery modules 19a to 19n for driving the motor 30 through an inverter 29. In order to detect the various voltages of the battery modules 19a to 19n, voltage detection circuits 40a to 40n are provided for the battery modules 19a to 19n, respectively. Each voltage detection circuit 40 includes a differential amplifier 2 for detecting the electric potential across the end terminals of the battery module 19, and the detected voltage of the battery module is digitized with an A/D converter 3. The voltage relating data thus obtained is then output to the vehicle-side electric circuit system for driving the engine, which has a different ground potential than that of the high-voltage electric circuit system and is electrically insulated therefrom, through a photo-coupler 7. The operating power for the voltage detection circuits 40a to 40n has to be supplied independently because the potential of these circuits measured from ground is different. Therefore, a power source 15 supplies operating power separately through a transformer having separate windings for each of the voltage detection circuits 40a to 40n. 
The above-described prior art battery voltage detecting device had the following problems:
(1) Since the voltage detection circuits 40 are always connected to the battery modules 19, leak currents flow from the battery modules 19 also when voltage is not being detected, and the batteries are discharged even when the battery power source device is not in use.
(2) Since the voltage detection circuits 40a to 40n operate at separate ground potentials, a power source 15 for supplying operating power separately is required. However, the power supplied from the power source 15 tends to be affected by common mode noise, resulting in errors in the voltage detection due to the influence of noise.
It is an object of the present invention to provide a battery voltage detecting device, in which there are no leak currents from battery modules. It is another object of the invention to provide a battery voltage detecting device without a power source that is susceptible to the effect of noise.
To achieve the above-mentioned objects, the present invention provides a battery voltage detecting device provided in a battery power source device used as a drive power source of an electric motor for a vehicle, wherein a plurality of rechargeable battery cells are serially connected to constitute a battery pack. The cells are divided into a plurality of groups each including a predetermined number of serially connected cells to form a plurality of battery modules. The battery pack is mounted on the vehicle with its ground potential being electrically insulated from ground potential of an electric circuit system of a controller for the vehicle. The battery voltage detecting device according to one aspect of the invention includes: a plurality of voltage detection circuits, respectively provided to the plurality of battery modules, each of the plurality of voltage detection circuits including a differential detecting means for detecting voltage across end terminals of a battery module, open/close means which open and close for connecting and disconnecting the differential detecting means to and from the end terminals of the battery module, an A/D converter for digitizing detected voltage of the battery module output from the differential detecting means, an output data transmission means for transmitting data output from the A/D converter to the electric circuit system of the controller for the vehicle in electrical insulation therefrom, and an open/close signal transmission means for transmitting an open/close signal output from the electric circuit system of the controller for the vehicle to the open/close means in electrical insulation therefrom; and an operating power source electrically insulated from the ground potential of the electric circuit system of the controller for the vehicle for providing each of the voltage detection circuits separately with operating power.
According to this arrangement, an open/close means is provided between the differential detecting means and the end terminals of a battery module, and the open/close means operates upon input of an open/close control signal from an open/close signal transmission means to connect the differential detecting means to the end terminals of the battery module only during the detection of voltage thereof. Accordingly, the differential detecting means is disconnected from the end terminals of the battery module except when voltage is detected, whereby wasteful discharge of the battery module due to leak currents is eliminated.
The battery voltage detecting device according to another aspect of the invention includes a plurality of voltage detection circuits, each provided to a unit of a plurality of battery modules, each of the plurality of voltage detection circuits including a differential detecting means connected through a detection switching circuit to the unit of the plurality of battery modules for detecting voltage across end terminals of a selected one of the plurality of battery modules, an A/D converter for digitizing detected voltage of the battery module output from the differential detecting means, an output data transmission means for transmitting data output from the A/D converter to the electric circuit system of the controller for the vehicle in electrical insulation therefrom, an open/close signal transmission means for transmitting an open/close signal output from the electric circuit system of the controller for the vehicle to the detection switching circuit in electrical insulation therefrom; and an operating power source electrically insulated from the ground potential of the electric circuit system of the controller for the vehicle for providing each of the voltage detection circuits separately with operating power. The detection switching circuit includes a plurality of open/close means which open and close for respectively connecting and disconnecting the differential detecting means to and from the respective end terminals of the plurality of battery modules, and open/close control means for separately open and close a selected one of the plurality of open/close means in accordance with the open/close control signal input from the open/close signal transmission means, whereby the selected one of open/close means is closed to connect the differential detecting means to the end terminals of the selected one of the battery modules.
According to this arrangement, a common voltage detection circuit, including a differential detecting means, an A/D converter, and an output data transmission means, is provided to a unit of a plurality of battery modules. A detection switching means having open/close means switchably connects the differential detecting means to the end terminals of a selected one of the battery modules in accordance with a signal from the open/close signal transmission means. The number of the voltage detection circuits is thus reduced. Also, since the differential detecting means is disconnected from the end terminals of the battery module except when voltage is detected, whereby wasteful discharge of the battery module due to leak currents is eliminated.
The battery voltage detecting device according to a further aspect of the invention includes a plurality of voltage detection circuits, respectively provided to the plurality of battery modules, each of the plurality of voltage detection circuits including a differential detecting means for detecting voltage across end terminals of a battery module, a first voltage conversion means for supplying the differential detecting means with operating power by transforming the voltage of the battery module, an A/D converter for digitizing detected voltage of the battery module output from the differential detecting means, a second voltage conversion means for supplying the A/D converter with operating power by transforming the voltage of the battery module, an output data transmission means for transmitting data output from the A/D converter to the electric circuit system of the controller for the vehicle in electrical insulation therefrom.
According to this arrangement, the differential detecting means and the A/D converter are provided with operating power with the first and second voltage conversion means which transform the voltage of the battery module, and hence an additional power source for supplying operating power to the differential detecting means and the A/D converter is not required. Thereby, the voltage detection circuit is prevented from being affected by common mode noise resulting from such additional power source which may cause erroneous voltage detection.
The battery voltage detecting device according to another aspect of the invention includes: a plurality of voltage detection circuits, respectively provided to the plurality of battery modules, each of the plurality of voltage detection circuits including a differential detecting means for detecting voltage across end terminals of a battery module, open/close means which open and close for connecting and disconnecting the differential detecting means to and from the end terminals of the battery module, a first voltage conversion means for supplying the differential detecting means with operating power by transforming the voltage of the battery module, an A/D converter for digitizing detected voltage of the battery module output from the differential detecting means, a second voltage conversion means for supplying the A/D converter with operating power by transforming the voltage of the battery module, an output data transmission means for transmitting data output from the A/D converter to the electric circuit system of the controller for the vehicle in electrical insulation therefrom, and an open/close signal transmission means for transmitting an open/close signal output from the electric circuit system of the controller for the vehicle to the open/close means in electrical insulation therefrom.
According to this arrangement, an open/close means is provided between the differential detecting means and the end terminals of a battery module, and the open/close means operates upon input of an open/close control signal from an open/close signal transmission means to connect the differential detecting means and the end terminals of the battery module only during the detection of voltage thereof. Accordingly, the differential detecting means is disconnected from the end terminals of the battery module except when voltage is detected, whereby wasteful discharge of the battery module due to leak currents is eliminated. Also, the differential detecting means and the A/D converter are provided with operating power with the first and second voltage conversion means which transform the voltage of the battery module, and hence an additional power source for supplying operating power to the differential detecting means and the A/D converter is not required. Thereby, the voltage detection circuit is prevented from being affected by common mode noise resulting from such additional power source which may cause erroneous voltage detection.
The battery voltage detecting device according to yet another aspect of the invention includes: a plurality of voltage detection circuits, each provided to a unit of a plurality of battery modules, each of the plurality of voltage detection circuits including a differential detecting means connected through a detection switching circuit to the unit of the plurality of battery modules for detecting voltage across end terminals of a selected one of the plurality of battery modules, a first voltage conversion means for supplying the differential detecting means with operating power by transforming the voltage of the battery module, an A/D converter for digitizing detected voltage of the battery module output from the differential detecting means, a second voltage conversion means for supplying the A/D converter with operating power by transforming the voltage of the battery module, an output data transmission means for transmitting data output from the A/D converter to the electric circuit system of the controller for the vehicle in electrical insulation therefrom, an open/close signal transmission means for transmitting an open/close signal output from the electric circuit system of the controller for the vehicle to the detection switching circuit in electrical insulation therefrom, wherein the detection switching circuit includes a plurality of open/close means which open and close for respectively connecting and disconnecting the differential detecting means to and from the respective end terminals of the plurality of battery modules, and open/close control means for separately open and close a selected one of the plurality of open/close means in accordance with the open/close control signal input from the open/close signal transmission means, whereby the selected one of open/close means is closed to connect the differential amplifier to the end terminals of the selected one of the battery modules.
According to this arrangement, a common voltage detection circuit, including a differential detecting means, an A/D converter, and an output data transmission means, is provided to a unit of a plurality of battery modules. A detection switching means having open/close means switchably connects the differential detecting means to the end terminals of a selected one of the battery modules in accordance with a signal from the open/close signal transmission means. The number of the voltage detection circuits is thus reduced. Also, since the differential detecting means is disconnected from the end terminals of the battery module except when voltage is detected, whereby wasteful discharge of the battery module due to leak currents is eliminated. Also, the differential detecting means and the A/D converter are provided with operating power with the first and second voltage conversion means which transform the voltage of the battery module, and hence an additional power source for supplying operating power to the differential detecting means and the A/D converter is not required. Thereby, the voltage detection circuit is prevented from being affected by common mode noise resulting from such additional power source which may cause erroneous voltage detection.